1. Field
One or more embodiments relate to thermoelectric materials having a high figure-of-merit, thermoelectric modules including the thermoelectric materials, and thermoelectric apparatuses including the thermoelectric modules, and more particularly, to dichalcogenide thermoelectric materials having a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity, thermoelectric modules including the thermoelectric materials, and thermoelectric apparatuses including the thermoelectric modules.
2. Description of the Related Art
Thermoelectric materials can be applied in active cooling and cogeneration using the Peltier effect and Seebeck effect. The Peltier effect refers to a phenomenon whereby, when an external DC voltage is applied as illustrated in FIG. 1, holes in a p-type material and electrons in an n-type material are transported and thus one end of each of the respective materials absorbs heat and the other end of the materials releases heat. The Seebeck effect refers to a phenomenon whereby, when heat is supplied by an external heat source as illustrated in FIG. 2, electrons and holes are transported and thus current flows in a material, thereby generating power.
Active cooling with a thermoelectric material can improve the thermal stability of a device, does not generate vibration and noise, and does not use a separate condenser or refrigerant. As a result, thermoelectric active cooling is regarded as an environmentally friendly method of cooling that is suitable for small devices. Active cooling with thermoelectric materials can be applied in refrigerators or air conditioners that do not include refrigerants, and various other micro-cooling systems. Further, a uniform, stable temperature may be obtained. Accordingly, the performance of the device may be improved.
In addition, if the Seebeck effect and thermoelectric materials are used for thermoelectric power generation, waste heat may be used as an energy source. Accordingly, the energy efficiency of car engines or exhausts may be improved. Also, electrical power may be generated from waste incinerators or from the waste heat of ironworking. In addition, the efficiency of a power source for a medical device, which uses body heat and is installed inside the body, may be increased. Thus waste heat may be collected and used in various applications.
A factor for evaluating the performance of a thermoelectric material is a dimensionless figure-of-merit ZT that is defined by Equation 1:
                    ZT        =                                            S              2                        ⁢            σ            ⁢                                                  ⁢            T                    k                                    Equation        ⁢                                  ⁢        1            where S is a Seebeck coefficient, a is electrical conductivity, T is an absolute temperature, and k is thermal conductivity.
To increase the dimensionless figure-of-merit ZT, there is a need to search for a material that has a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity.